Can you make a cupcake swirl using royal icing?

I’m sorry to say that you can not use royal icing to do a swirl on top of a cupcake. Royal icing, in baking, is mainly used as a glue or an adhesive. The type of frosting in that picture is a chocolate butter cream frosting. It is thick enough to frost onto cupcakes, and it has a very nice texture to it. Hope this helped! Good luck with the bake sale! :D